Such a method is known from U.S. Pat. No. 7,480,100 in which it is disclosed to apply a number of interlaced pictures onto the image layer of a lenticular structure for displaying three-dimensional, animated and other images. The lenticular structure may comprises a number of line-shaped lenses. A number of 10-30 interlaced images is formed and the pixel tracks of these images are interlaced and printed below the lenses with the pitch of the lens system such that one set of interlaced pixel tracks may be located each time below a single line-shaped lens. Depending on the angle of viewing, one of the interlaced images is observed by the viewer, and by tilting the lenticular structure, different images are viewed.
In a favourable embodiment, the images on the lenticular structure may comprise multiples of two portraits of a person taken at different angles, which are interlaced such that sets of two images are produced that are separately viewed by each respective eye of a viewer at a range of viewing distances of for instance 20-100 cm. In this manner a stereoscopic effect is achieved through the range of viewing distances.
The interlaced images may be printed on a substrate, for instance polycarbonate, where after the line-shaped lens structure may be applied over each set of interlaced pixel tracks using a die or mould. Alternatively, the lens structure is first formed and the interlaced images are subsequently written onto the substrate by means of a scanning optical beam, such as a laser.
A disadvantage of using a number of interlaced images is that upon viewing these images via the lenticular device, patterns of dark shading appear to run across the image when changing the angle of view. This produces an unstable visual effect which especially for the use of the lenticular device as a security device hinders accurate and reliable identification.
It is hence an object of the invention to provide a lenticular device in which the above effect is reduced. It is another object of the invention to provide a lenticular device which is especially suitable for producing accurate and reliable identity or security document.